Mantle redox state drives outgassing chemistry and atmospheric composition of rocky planets.

Volcanic degassing of planetary interiors has important implications for their corresponding atmospheres. The oxidation state of rocky interiors affects the volatile partitioning during mantle melting and subsequent volatile speciation near the surface. Here we show that the mantle redox state is central to the chemical composition of atmospheres while factors such as planetary mass, thermal state, and age mainly affect the degassing rate. We further demonstrate that mantle oxygen fugacity has an effect on atmospheric thickness and that volcanic degassing is most efficient for planets between 2 and 4 Earth masses. We show that outgassing of reduced systems is dominated by strongly reduced gases such as [Formula: see text], with only smaller fractions of moderately reduced/oxidised gases ([Formula: see text], [Formula: see text]). Overall, a reducing scenario leads to a lower atmospheric pressure at the surface and to a larger atmospheric thickness compared to an oxidised system. Atmosphere predictions based on interior redox scenarios can be compared to observations of atmospheres of rocky exoplanets, potentially broadening our knowledge on the diversity of exoplanetary redox states.

Review on the Role of Planetary Factors on Habitability.

In this work various factors on the habitability were considered, focusing on conditions irrespective of the central star's radiation, to see the role of specific planetary body related effects. These so called planetary factors were evaluated to identify those trans-domain issues where important information is missing but good chance exit to be filled by new knowledge that might be gained in the next decade(s). Among these strategic knowledge gaps, specific issues are listed, like occurrence of radioactive nucleides in star forming regions, models to estimate the existence of subsurface liquid water from bulk parameters plus evolutionary context of the given system, estimation on the existence of redox gradient depending on the environment type etc. These issues require substantial improvement of modelling and statistical handling of various cases, as "planetary environment types". Based on our current knowledge it is probable that subsurface habitability is at least as frequent, or more frequent than surface habitability. Unfortunately it is more difficult from observations to infer conditions for subsurface habitability, but specific argumentation might help with indirect ways, which might result in new methods to approach habitability in general.

PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS.

The Interuniversity Attraction Pole (IAP) 'PLANET TOPERS' (Planets: Tracing the Transfer, Origin, Preservation, and Evolution of their Reservoirs) addresses the fundamental understanding of the thermal and compositional evolution of the different reservoirs of planetary bodies (core, mantle, crust, atmosphere, hydrosphere, cryosphere, and space) considering interactions and feedback mechanisms. Here we present the first results after 2 years of project work.

Habitability: A Review.

Habitability is a widely used word in the geoscience, planetary science, and astrobiology literature, but what does it mean? In this review on habitability, we define it as the ability of an environment to support the activity of at least one known organism. We adopt a binary definition of "habitability" and a "habitable environment." An environment either can or cannot sustain a given organism. However, environments such as entire planets might be capable of supporting more or less species diversity or biomass compared with that of Earth. A clarity in understanding habitability can be obtained by defining instantaneous habitability as the conditions at any given time in a given environment required to sustain the activity of at least one known organism, and continuous planetary habitability as the capacity of a planetary body to sustain habitable conditions on some areas of its surface or within its interior over geological timescales. We also distinguish between surface liquid water worlds (such as Earth) that can sustain liquid water on their surfaces and interior liquid water worlds, such as icy moons and terrestrial-type rocky planets with liquid water only in their interiors. This distinction is important since, while the former can potentially sustain habitable conditions for oxygenic photosynthesis that leads to the rise of atmospheric oxygen and potentially complex multicellularity and intelligence over geological timescales, the latter are unlikely to. Habitable environments do not need to contain life. Although the decoupling of habitability and the presence of life may be rare on Earth, it may be important for understanding the habitability of other planetary bodies.

B1 integrin activation inhibits in vitro tube formation: effects on cell migration, vacuole coalescence and lumen formation.

Human endothelial cells (EC), when plated onto gels of extracellular matrix proteins such as Matrigel or collagen form capillary tubes in a process thought to mimic angiogenesis. We have shown previously that the extent of tube formation and the phenotype of the lumen are regulated by integrins (Gamble et al 1993) and lumen formation occurs through a process of vacuolization, coalescence and ultimate directional fusion of these vacuoles with the plasma membrane (Meyer 1997 et al). We now show here that activation of beta1 integrins on endothelial cells inhibits tube formation. On collagen gels, endothelial cells treated with 31 activating antibody 8A2 failed to migrate into the gel and tube formation was inhibited. Although several integrins mediate EC attachment to collagen alpha2beta1 is the chief determinant of EC behaviour since a blocking antibody to (alpha2beta1 reversed the effect of 8A2. On Matrigel tube formation was also inhibited by 8A2 treatment although cell alignment and sprout formation was still evident. Electron microscopy revealed the organisation of normal numbers of cells into solid sprouts and the formation of small intracellular vacuoles suggesting that initial stages of tube formation including cell migration were unaffected. However, beta1 integrin activation inhibited the coalescence of these small vacuoles into larger vacuoles, the recruitment of more cells into the sprout and the subsequent formation of mature lumen. The inhibition of capillary tube formation by beta1 activation was time dependent and long lasting. The critical time for activation of the beta1 integrin was the initial 1-2h after plating in order to inhibit tube formation although once activated, the beta1 mediated inhibition on Matrigel was still evident 4 days later. Our results suggest that beta1 integrins are critical in capillary tube formation in at least two phases. beta1 integrins are essential for migration of EC through collagen gels. Independently, beta1 integrins, although not involved in initial vacuole formation, are involved in the process of vacuole coalescence and subsequent lumen formation since beta1 integrin activation inhibits these processes.

Novel cytokine-independent induction of endothelial adhesion molecules regulated by platelet/endothelial cell adhesion molecule (CD31).

Tumor necrosis factor-alpha, interleukin-1, and endotoxin stimulate the expression of vascular endothelial cell (EC) adhesion molecules. Here we describe a novel pathway of adhesion molecule induction that is independent of exogenous factors, but which is dependent on integrin signaling and cell-cell interactions. Cells plated onto gelatin, fibronectin, collagen or fibrinogen, or anti-integrin antibodies, expressed increased amounts of E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1. In contrast, ECs failed to express E-selectin when plated on poly-L-lysine or when plated on fibrinogen in the presence of attachment-inhibiting, cyclic Arg-Gly-Asp peptides. The duration and magnitude of adhesion molecule expression was dependent on EC density. Induction of E-selectin on ECs plated at confluent density was transient and returned to basal levels by 15 h after plating when only 7 +/- 2% (n = 5) of cells were positive. In contrast, cells plated at low density displayed a 17-fold greater expression of E-selectin than did high density ECs with 57 +/- 4% (n = 5) positive for E-selectin expression 15 h after plating, and significant expression still evident 72 h after plating. The confluency-dependent inhibition of expression of E-selectin was at least partly mediated through the cell junctional protein, platelet/endothelial cell adhesion molecule-1 (PECAM-1). Antibodies against PECAM-1, but not against VE-cadherin, increased E-selectin expression on confluent ECs. Co- culture of subconfluent ECs with PECAM-1- coated beads or with L cells transfected with full-length PECAM-1 or with a cytoplasmic truncation PECAM-1 mutant, inhibited E-selectin expression. In contrast, untransfected L cells or L cells transfected with an adhesion-defective domain 2 deletion PECAM-1 mutant failed to regulate E-selectin expression. In an in vitro model of wounding the wound front displayed an increase in the number of E-selectin-expressing cells, and also an increase in the intensity of expression of E-selectin positive cells compared to the nonwounded monolayer. Thus we propose that the EC junction, and in particular, the junctional molecule PECAM-1, is a powerful regulator of endothelial adhesiveness.

Lumen formation during angiogenesis in vitro involves phagocytic activity, formation and secretion of vacuoles, cell death, and capillary tube remodelling by different populations of endothelial cells.

BACKGROUND: We have utilised an in vitro model of angiogenesis to investigate the morphological changes which occur during the formation of a lumen in capillary tubes. METHODS AND RESULTS: On collagen 1 gel in the presence of phorbol myristate acetate (PMA) and anti-alpha 2 beta 1 antibody, cell aggregation and alignment takes place within two hours of plating. The initial apparently homogeneous population of endothelial cells (EC) actually display at least three distinct phenotypes. One population, characterised by a phagocytic phenotype, migrated through the gel creating channels and defines the extent of the capillary network. These are later enveloped by a second population of cells characterised by intracellular vacuoles. The ultimate fate of these vacuoles is fusion with the plasma membrane. By 12 hours the original phagocytic cell population undergoes cell death, which morphologically appears apoptotic in nature. A consequence of the secretion of vacuoles and programmed cell death is the extensive remodelling of the capillary tubes, resulting in expansion of the intercellular space into a lumen. The remodelling results in 45% of the EC membrane contacting the lumenal surface at the expense of EC-EC and EC-matrix contact. A third population of cells implant between the EC involved in lumen formation and thus expand the size of the capillary tube. CONCLUSION: Thus, in the formation of a mature multicellular lumen we have identified a number of key events. First, cell-cell contact is essential in order to define the intercellular space. Second, at least three morphologically distinct subpopulations of ECs are involved. Third, vacuole formation and programmed cell death are required for expansion of the intercellular space which ultimately becomes the lumen.

Transforming growth factor-beta 1 inhibits the production of IL-8 and the transmigration of neutrophils through activated endothelium.

A central mechanism of inflammation is the activation of vascular endothelium by the inflammatory cytokines TNF-alpha and IL-1. These cytokines induce the expression of adhesion molecules, the elaboration of chemokines, and the transendothelial migration of white cells. TGF-beta 1 has anti-inflammatory properties, is expressed in the vessel wall, and has previously been shown to inhibit leukocyte adhesiveness to the endothelium at least in part by inhibiting the expression of E-selectin. We now show that TGF-beta 1 also inhibits the migration of neutrophils through endothelial monolayers activated by TNF-alpha. At a dose of 10 U/ml TNF-alpha, the transmigration of neutrophils was inhibited 42.7 +/- 7.9% (n = 8) by 0.2 ng/ml TGF-beta 1. Furthermore, TGF-beta 1 inhibited, in a time- and dose-dependent fashion, the elaboration of IL-8 by TNF-activated endothelial cells by between 33 and 78% (TNF doses from 100 down to 0.1 U/ml) and the elaboration of mRNA for IL-8 by 69%. TGF-beta 1 treatment did not significantly alter the TNF-induced IL-8 mRNA stability, suggesting that the mechanism of action of TGF-beta 1 is on gene transcription. Neutrophil transmigration through cytokine-activated endothelium involves both IL-8-dependent and IL-8-independent mechanisms. Using an anti-IL-8 Ab, we show that TGF-beta 1 inhibits only the IL-8-dependent pathway, but does not affect the IL-8-independent transendothelial migration mechanism. These and our previous results show that TGF-beta1, achieves its anti-inflammatory properties by inhibiting the expression of at least two genes, E-selectin and IL-8, which are essential in the inflammatory pathway.

Chronic expression of P-selectin on endothelial cells stimulated by the T-cell cytokine, interleukin-3.

P-selectin expressed on the surface of endothelium mediates leukocyte adhesion in vitro and rolling in vivo. Several inducers of cell-surface P-selectin expression on endothelial cells (EC) have previously been identified, all of which yield transient cell-surface expression of P-selectin lasting minutes to a few hours. We now show that a T-lymphocyte product, interleukin-3 (IL-3), stimulates the long-term endothelial cells (HUVEC). IL-3 induced cell-surface P-selectin expression in two phases. An initial peak at 10 minutes was followed by a prolonged upregulation beginning 16 hours after IL-3 addition and lasting at least 4 days. The level of P-selectin expression induced by IL-3 added for 48 hours was similar to that induced by treatment of HUVEC for 10 minutes with thrombin, and the effect of adding IL-3 for 48 hours followed by thrombin for 10 minutes was additive. Induction of cell-surface P-selectin expression by IL-3 was blocked by pretreatment of EC with a blocking monoclonal antibody against the IL-3 receptor alpha-chain. Lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha) and a mutant form of IL-3 with decreased potency did not induce cell-surface P-selectin expression after 48 hours' incubation with HUVEC, suggesting that the effect was specific to IL-3. The increase in cell-surface P-selectin expression occurring after 16 hours of incubation with IL-3 was accompanied by a similar prolonged increase in the steady-state mRNA level that was not observed at 10 minutes after IL-3 addition. As T-lymphocyte infiltration is a hallmark of chronic inflammation, our observations suggest that the secretion of IL-3 by T lymphocytes may serve to maintain the inflammatory state during chronic inflammation.

TGF-beta and endothelial cells inhibit VCAM-1 expression on human vascular smooth muscle cells.

Vascular smooth muscle cells (VSMCs) are normally devoid of the adhesion protein vascular cell adhesion molecule-1 (VCAM-1), which has, however, been observed on human VSMCs in atheroma. We now show that cultured human saphenous vein VSMCs express small amounts of VCAM-1 and that the cytokine tumor necrosis factor-alpha (TNF-alpha) induces, in a time- and dose-dependent fashion, a significant increase in its expression. Interleukin (IL)-4, IL-1, and to a lesser extent interferon gamma have similar effects. TNF-alpha-stimulated human VSMCs demonstrate increased binding of T lymphocytes that is totally VCAM-1 mediated. The cytokine transforming growth factor-beta (TGF-beta) at 2.0 ng/mL inhibited basal VCAM-1 expression by 84 +/- 8% and the induction by TNF-alpha by between 56 +/- 16% and 77 +/- 15% depending on the dose of TNF. Furthermore, coculture on opposing sides of a polycarbonate filter of human VSMCs with human umbilical vein endothelial cells also inhibited the induction of VCAM-1 by 47 +/- 6%. As active TGF-beta is produced upon the coculture of VSMCs and endothelial cells, we suggest that the close physical proximity of these cells in vivo is responsible for the lack of expression of VCAM-1 on VSMCs and that the interruption of this contact in atheroma is an important pathogenic event. As VCAM-1 not only serves as an adhesion molecule but also as a costimulator of immune cells, its expression may be crucial in the propagation of vascular lesions.

Characterization of a spontaneously transformed human endothelial cell line.

BACKGROUND: A line of cells was isolated from a focus observed in a human umbilical vein endothelial cell (HUVEC) culture, presumably the result of a spontaneous transformation event. EXPERIMENTAL DESIGN: The cell line was continuously cultured for 16 months, after which time, the proliferative rate, capacity to be cloned, and ability to be transfected was investigated. The cell line was analyzed for expression of endothelial cell markers, von Willebrand Factor, P selectin, and scavenger receptor. We also examined the tumor necrosis factor (TNF)-mediated upregulation of E-selectin, vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. We evaluated the levels of expression and types of TNF-alpha receptor expressed by the cell line, and the cell lines response to interleukin-4 and interferon-gamma. CD34 expression of this cell line and the ability of transforming growth factor-beta to inhibit the TNF-alpha induction of E-selectin was examined. The ability to support neutrophil adhesion and transmigration, and generate capillary-like tubes in vitro was assessed. Finally, the karyotype and tumourigenicity of this line was established. RESULTS: This cell line (C11STH) has a doubling time comparable to that of normal HUVECs and has a trisomy of chromosome 8 and 11. The cell line is capable of generating colonies at clonal density, and is transfectable with efficiencies comparable to normal HUVECs. C11STH expresses von Willebrand factor, P-selectin, and scavenger receptor to an extent similar to passaged HUVECs and can be induced to express E-selectin, VCAM, and ICAM with TNF-alpha. C11STH expresses both the p55 and p75 subunits of TNF-alpha receptor at levels similar to HUVECs. The ability of interleukin-4 to enhance the expression of VCAM and reduce the TNF-alpha-mediated expression of E-selectin is maintained in this cell line. C11STH cells are unable to induce class II major histocompatibility antigen in response to interferon-gamma. However, interferon-gamma is able to synergize with TNF to enhance the expression of E-selectin. C11STH cells do not express CD34 or show transforming growth factor-beta inhibition of TNF-alpha induced E-selectin expression, functions indicative of primary, or early passage HUVECs. The cell line retains the ability to support neutrophil adhesion and transmigration and can generate patent tubes when seeded onto complex basement membrane gels. However, the cell line no longer has the ability to generate capillary-like vessels when seeded onto collagen gels in the presence of phorbol 12-myristate 13-acetate. CONCLUSIONS: C11STH has retained many of the normal characteristics of endothelial cells, is able to proliferate at clonal density, and is easily transfectable. The line will provide a useful resource for endothelial cell biology. Its ability to make capillary-like tubes on basement membrane gels, but not on collagen will provide a powerful tool with which to further analyze the processes involved in angiogenesis, and will enable us to define the role of specific proteins in angiogenesis. Since C11STH shows tube competence on Matrigel, but is not tube competent on collagen, our studies suggest that capillary-tube formation on Matrigel and collagen occur via qualitatively different mechanisms. Thus, this cell line provides the opportunity to examine the signalling mechanisms required to generate capillary tube formation. These may include the involvement of matrix molecules, the production of proteases and inhibitors, gene regulation and kinases or phosphatases.

Donor cornea procurement: six-year review of the role of the eye bank in South Australia.

The Lions Eye Bank of South Australia was established six years ago and has collected corneas from 790 donors. The consent rate is currently 82% of requests made. Two-thirds of donors have been male, with mean donor age/year varying from 54 to 64 years (range two to 93 years). Cardiovascular and respiratory diseases, trauma and haemorrhage account for 80% of all donor deaths. Mean death to enucleation time is five hours. Corneas assessed as being of excellent or very good quality are released preferentially from the bank; those with central endothelial cell counts of less than 1500 cells/mm2 are discarded. Fewer than 1% of donors have returned a positive result for HIV or hepatitis B. Of the 1580 corneas collected by the bank, 863 (55%) have been used for transplantation with a primary non-function rate of 0.46%. The evolving policies, logistics of operation and methodologies employed by the bank are described in detail.

Experimental studies on caustic burns of the stomach by aggressive chemicals.

The treatment of caustic burns of the stomach in childhood by acids, alkalis and especially soldering fluids has remained without any clear concept so far. Surgical treatment consists of therapy of acute complications or late sequelae. Early endoscopy enables one to decide between conservative treatment and early laparotomy. Animal experiments were performed in albino rats for the development of a therapeutic concept. Because of its amphoteric and aggressive nature, soldering fluid zinc dissolved in 33-50 M saline) was used as the caustic substance. Clear demarcation and tissue changes can be recognized after 6-8 h, at the earliest. Laparotomy aiming at protective plication or atypical gastric resection should be performed at that time, if endoscopy reveals a third-degree caustic burn of the stomach.

Assessment of the Dutch organ-culture system of corneal preservation within the Eye Bank of South Australia.

Thirteen per cent of all corneas harvested by the Eye Bank of South Australia during 1986 were discarded because storage time in McCarey-Kaufman medium exceeded four days. We have therefore examined the suitability of the Dutch method of long-term corneal storage for our purposes. Twenty-two human corneas that had been discarded from the Eye Bank were assessed using the trypan blue-sucrose staining technique, and then placed into long-term storage for 15 to 17 days. They were then reassessed by vital dye staining before permanent flat-mounts were prepared for silver staining of the endothelium. A good correlation (albeit subjective) was found between the non-destructive and destructive techniques of endothelial cell assessment. Those corneas that failed to survive organ culture storage were easily detected. The Dutch system of corneal preservation and post-storage assessment seems well-suited to Australian eye-banking.